IRTF PRIMO Photometers

The IRTF PRIMO Photometers are high sensitivity InSb photometers with passbands defined by a set of discrete filters and a circular variable filter (CVF) segment (in PRIMO1) or by two CVFs (in PRIMO2). Data is recorded automatically by the IBM PC Data Aquisition System (DAS) computer, which controls filter and aperture changes remotely from the control room.

Filters and Apertures

The discrete filters available for use with PRIMO1, and associated sensitivities, are listed below:

Filter	Lambda (µm)	Delta Lambda (µm)	Limiting Mag	Limiting Flux (µJy)
1	J (1.25)	0.30	21.8	3.1
2	H (1.65)	0.35	20.9	4.6
3	K (2.20)	0.42	20.6	3.8

Notes:

• Limiting mags and fluxes are for 1 sigma detections (S/N=1) in a 6 arcsec aperture in 1 hour of integration with good sky conditions.

The available apertures are circular with diameters (mm) of:

Aperture Diameters (mm)
0.5	1.0	1.5	2.0	3.0	4.0	5.0	6.0	7.0